A vehicle consists of one rigid body for the Chassis and several Wheels.

Using rays for wheels: Each wheel is a ray that samples the ground. This is very efficient and allows for tuning and artificial behavior. It is also more stable, because there are no constraints between the car and wheel bodies which could be violated. The disadvantage is that the wheel movement is not smooth when moving over non-smooth terrain (e.g. steps).

The forward direction of the vehicle is the -z direction.